[signin] Fix regression in MergeSigninCredentialIntoCookieJar

The CL https://chromium-review.googlesource.com/c/chromium/src/+/1104682/9/components/signin/core/browser/signin_manager.cc
introduced a regression, leading to cookies not being merged correctly.
The cookies should be merged in all cases except Mirror, but that CL
did the opposite (only merging cookies when Mirror is enabled)

Change-Id: Ib3c5454259ff6b7ec82bb2411bcff011bc63f3e1
Bug: 777774
Reviewed-on: https://chromium-review.googlesource.com/1109976Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569287}

components/signin/core/browser/signin_manager.cc

@@ -393,8 +393,7 @@ void SigninManager::DisableOneClickSignIn(PrefService* prefs) {
 }
 
 void SigninManager::MergeSigninCredentialIntoCookieJar() {
-#if !defined(OS_IOS)
-  if (account_consistency_ != signin::AccountConsistencyMethod::kMirror)
+  if (account_consistency_ == signin::AccountConsistencyMethod::kMirror)
     return;
 
   if (!IsAuthenticated())
@@ -402,7 +401,6 @@ void SigninManager::MergeSigninCredentialIntoCookieJar() {
 
   cookie_manager_service_->AddAccountToCookie(GetAuthenticatedAccountId(),
                                               "ChromiumSigninManager");
-#endif  // !defined(OS_IOS)
 }
 
 void SigninManager::CompletePendingSignin() {